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Champ S+ Repair Question

#1
I have a Champ S+ and one windy day it cartwheeled down a field shredding pieces along the way. It wasn't in terrible shape, I glued it all back together. When I glued down the horizontal stab/elevator I made sure the elevator servo was centered, and glued it down so the elevator lined up with the horizontal stab.

When I test flew it things seemed okay until I cut the throttle to idle, and it nosedived straight down, hit the ground and broke the 10th prop adapter I've made for it.

My question is, can someone with a Champ S+ (that is trimmed out and flies well) please boot it up, put in acro mode with elevator stick centered and see if the elevator is inline with the horizontal stab?

I think that the neutral elevator position must be a little elevator up, and not inline with the stab. I've checked the CG and everything else. It seems to be a trim issue. I just don't want to crash it testing new trim positions. Thanks.
 

Ketchup

4s mini mustang
#2
Do you have any pictures of the plane, because it would be much easier to help with a visual, but I do have some ideas on what might have gone wrong. Have you checked the cg of the plane (center of gravity, it should be about a quarter of the way back from the leading edge of the wing), because your plane could be tail heavy, and also, how much weight did you add in repairs, because I used to have a plane that was underpowered and flew right above it’s stall speed, so it stalled as soon as I cut the throttle. I hope I helped in some way, good luck!
 
#3
Thanks Ketchup! CG is good. I didn't add much weight in glue. I weighed the airplane and it weighs less than stock, not sure how that happened. I would assume if I added too much weight to the tail the CG would be off, so I don't think that is it. The Champ manual doesn't show much in the way of mechanical setup...

What I'm asking is pictured below. If someone with a working Champ S+ can boot theirs up, don't adjust your trims, make sure it is in full acro mode, while holding it very still look at the alignment of the elevator in relation to the horizontal stab (yellow line in pic).

Is it flush as pictured?

I'm leaning toward no, there must be some back elevator for the neutral position. I believe that would fix my problem. However, I don't seem to remember it not being lined up, so maybe it is something else, but I'm out of other stuff to check. I also don't have a nice soft place to crash on test flights, so I'm hoping to get this ironed out on the ground.


IMG_2395.JPG
 

JTarmstr

Well-known member
#4
When it cartwheeled, was there any damage to the wing? The wing incidence might be off. That can cause bad nosedives.
 

Ketchup

4s mini mustang
#6
@SoCalPilot, I know that this is an odd question, and that you probably already did this, but have you tried throttling the plane all the way up, and then back down to zero while watching the elevator. Your transmitter might have some elevator/throttle mixing on it which could make the plane dive without throttle
 
#7
When it cartwheeled, was there any damage to the wing? The wing incidence might be off. That can cause bad nosedives.
Thanks. The wings are intact and seem okay. It does fly well under power. I like to be able to cut the throttle and glide, and right now if I do that, down she goes!
 
#8
@SoCalPilot, I know that this is an odd question, and that you probably already did this, but have you tried throttling the plane all the way up, and then back down to zero while watching the elevator. Your transmitter might have some elevator/throttle mixing on it which could make the plane dive without throttle
That's not an odd question at all. I've been known to setup mixes like that, and I've been known to mix up my mixes. I checked and there are no mixes, confirmed with the model itself.
 

Ketchup

4s mini mustang
#9
Ooohhhhh... I just realized, THRUST ANGLE!!!! The plane’s motor could have been knocked up or down during the cartwheel, so maybe check the thrust angle and see if the motor is secure.
 
#10
The motor mount and motor held up well. I guess that is one benefit of a weak prop adapter. Speaking of which I attached the STL if anyone needs a Champ Prop adapter. No license, feel free to do whatever you want with it.
 

Attachments

Bricks

Well-known member
#12
I am pondering your question and cannot seem to come up with a definitive answer. The only thing is that it is nose heavy, once airspeed is lost it dives. With air speed there is enough flow over the elevator to keep it flying. My elevator on my Cub Sport S is level. I would double check the CG. These things are so small I would use something besides my fingers to check CG
 

Merv

Well-known member
#13
CG, wing incident & thrust angle are all capable of causing this problem and all would be suspect after a crash. Another suspect could be a gyro in your SAFE. Does SAFE on or off change any behavior?

It would be best to find the problem and fix it. Bit a work around would be to mix throttle to elevator. To give it up elevator when throttle is off.
 

d8veh

Well-known member
#14
Yes, there are too many possible causes: Battery connection; failsafe engaging; SAFE+ attempting something; etc. Many would be eliminated if it dived every time you cut the throttle.
 
#15
Thanks everyone. It flies well in Safe Beginner mode. CG has been checked a bunch of times. I thought maybe the CG was shifting in flight but that's not the case either.

I adjusted the neutral point of the elevator so when the stick is centered there is some back pressure. I will go test fly it ASAP and report back.
 
#16
It flew fine today. The elevator was lined up with the h. stab with the stick neutral, and it didn't nose dive at idle. I have no idea why it was doing that. Thanks for the help!